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Abstract Detail



Pollination Biology

Harder, Lawrence David [1], Richards, Shane A. [2], Ågren, Jon [3], Johnson, Steven D. [4].

Multiple mechanisms of male-male interference during pollen dispersal for an orchid, Anacamptis morio.

Male gametophytes live highly competitive lives, vying for access to stigmas, to stylar resources and to ovules. In contrast to competition that occurs once pollen reaches stigmas, the occurrence of competition during dispersal and its underlying mechanisms are poorly documented, in part because of difficulties tracking pollen during dispersal. In principle, pollen from sequentially visited donor flowers of an animal-pollinated species could interact during dispersal by affecting i) whether other pollen remains on a pollinator between flower visits (residence), ii) whether pollen contacts the stigmas of subsequently visited flowers (contact), and/or iii) the amount of pollen transferred to individual stigmas (transfer). We assessed the incidence of interference and the contributions of these mechanisms for a bee-pollinated orchid, Anacamptis morio, by staining the paired sectile (massulate) pollinia of individual donor flowers and tracking the fates of stained massulae during subsequent visits by bumble bees to potential recipient flowers. During separate trails, recipient flowers could either contribute their own pollinaria (intact) to that carried by the pollinator, and so could interfere with the tracked donor pollen, or had previously been emasculated, so that donor pollen was transported in isolation. The resulting dispersal data were fit to 18 alternative mechanistic models to assess the relative contributions of the possible three interference processes. Donor pollen reached stigmas of up to 16 recipient flowers, indicating considerable pollen carryover. More than twice as many donor pollinaria remained attached to bees after intact trials than after emasculated trials, indicating that the addition of pollinaria to a pollinator by subsequently-visited flowers promoted residence of donor pollen during transport. Nevertheless, bees dispersed 26% fewer stained massulae during intact trials than during emasculated trials, indicating significant pollen interference during interaction with stigmas. Several statistical models fit the data adequately, precluding unique identification of the contributions of individual mechanisms. However, when treatment effects were detected for a parameter, the nature of the effect was always consistent: interference reduced pollinium contact with stigmas, reduced massulae transfer to stigmas during flower visits, increased among-flower variation in deposition within trials, and/or increased variation in deposition among trials. That interference during pollinator-stigma interactions overwhelms the benefits of greater pollinarium residence highlights the importance of traits that govern pollen exchange from pollinator to stigma in determining siring success.


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1 - University Of Calgary, Department Of Biological Sciences, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
2 - Durham University, School of Biological and Biomedical Sciences, South Road, Durham, DH1 3LE, UK
3 - Uppsala University, Dept. of Plant Ecology and Evolution, Evolutionary Biology Centre, Norbyvagen 18 D, Uppsala, N/A, SE-752 36, Sweden
4 - University of KwaZulu-Natal, School of Biological and Conservation Sciences, Private Bag X01 Scottsville, Pietermaritzburg, KwaZulu-Natal, 3209, South Africa

Keywords:
pollen competition
pollen dispersal
orchid.

Presentation Type: Oral Paper:Papers for Topics
Session: 8
Location: Salon 6/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 11:15 AM
Number: 8012
Abstract ID:831
Candidate for Awards:None


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